Bromodomain-containing protein 4 (BRD4) is a pivotal transcriptional regulator implicated in cancer, fibrosis, and inflammation, yet its phospho-regulatory network remains underexplored. This study leverages an extensive analysis of 1000 qualitative and 225 quantitative global phosphoproteome datasets to decode the BRD4 phosphorylation landscape. We identified S601 and S1117 as predominant phosphorylation sites, driving the majority of BRD4 phospho-signaling. Co-regulation analysis revealed 755 and 972 proteins positively cophosphorylated with S601 and S1117, respectively, including key interactors like TRIM28 (S473) and PRKAR2A (S78), which enhance transcriptional activity and cAMP signaling. Upstream kinases MAPK14 and GRK5 emerged as high-confidence regulators of S1117 and S601, respectively, with correlations in breast cancer highlighting disease relevance. In addition, 93 phosphosites in 71 transcription factors co-regulated with S1117 and 69 in 53 with S601 underscore the role of BRD4 in transcription control. These findings unveil a complex phospho-signaling network, offering novel therapeutic targets for BRD4-associated diseases and a foundation for future experimental validation.
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